Independent gate FinFET with backside gate contact

ABSTRACT

A method of making a semiconductor device includes forming a plurality of fins on a substrate, with the substrate including an oxide layer arranged beneath the plurality of fins. A sacrificial gate material is deposited on and around the plurality of fins. First trenches are formed in the sacrificial gate material. The first trenches extend through the oxide layer to a top surface of the substrate and are arranged between fins of the plurality of fin. First trenches are filled with a metal gate stack. Second trenches are formed in the sacrificial gate material, with a bottom surface of the second trenches being arranged over a bottom surface of the first trenches, and the second trenches being arranged between fins of the plurality of fins and alternating with the first trenches. The second trenches are filled with a metal gate stack.

PRIORITY

This application is a division of and claims priority from U.S. patentapplication Ser. No. 15/441,941, filed on Feb. 24, 2017, entitled“INDEPENDENT GATE FINFET WITH BACKSIDE GATE CONTACT,” the entirecontents of which are incorporated herein by reference.

BACKGROUND

Embodiments of the present invention relate to complementary metal oxidesemiconductor (CMOS) technology, and more specifically, to independentgates in FinFET devices.

CMOS technology is used to construct integrated circuits such asmicroprocessors, microcontrollers, static random access memory (RAM) andother digital logic circuits. A basic component of CMOS designs is metaloxide semiconductor field effect transistors (MOSFETs).

The FinFET is a type of MOSFET. The FinFET is a double-gate ormultiple-gate MOSFET device that mitigates the effects of short channelsand reduces drain-induced barrier lowering. The “fin” refers to thenarrow channel between source and drain regions. A thin dielectric layeron either side of the fin separates the fin channel from the gate.

SUMMARY

According to one or more embodiments, a method of making a semiconductordevice includes forming a plurality of fins on a substrate, thesubstrate including an oxide layer beneath the plurality of fins. Asacrificial gate material is deposited on and around the plurality offins. First trenches are formed in the sacrificial gate material. Thefirst trenches extend through the oxide layer to a top surface of thesubstrate and are arranged between fins of the plurality of fin. Firsttrenches are filled with a metal gate stack. Second trenches are formedin the sacrificial gate material, with a bottom surface of the secondtrenches being arranged over a bottom surface of the first trenches, andthe second trenches being arranged between fins of the plurality of finsand alternating with the first trenches. The second trenches are filledwith a metal gate stack.

According to other embodiments, a method of making a semiconductordevice includes forming a plurality of fins on a substrate, thesubstrate including an oxide layer beneath the plurality of fins. Asacrificial gate material is deposited on and around the plurality offins. First trenches are formed in the sacrificial gate material, withthe first trenches extending through the oxide layer to a top surface ofthe substrate and being arranged between fins of the plurality of fins.First trenches are filled with a metal gate stack. Second trenches areformed in the sacrificial gate material, with a bottom surface of thesecond trenches being arranged over a bottom surface of the firsttrenches, and the second trenches being arranged between fins of theplurality of fins and alternating with the first trenches. Secondtrenches are filled with a metal gate stack. Metal gate stacks of thefirst trenches are recessed, and a dielectric material is deposited on arecessed region of the metal gate stack of the first trenches. A metalis deposited on the metal gate stacks of the second trenches and thedielectric material of the first trenches to connect the metal gatestacks of the second trenches, with the metal gate stacks of the firsttrenches being isolated from the metal gate stacks of the secondtrenches by the dielectric material.

Yet, according to other embodiments, a semiconductor device includes asubstrate, with an oxide layer arranged on the substrate. Thesemiconductor device includes a fin extending from the substrate, and agate formed on the fin that extends substantially perpendicular to thefin. The gate includes a dielectric cap on a top surface of the gate.The gate includes alternating first portions and second portions, withthe first portions arranged below the second portions. The firstportions contact the substrate and extend through the oxide layer todielectric layers that are beneath the dielectric ca. The secondportions extend from a top surface of the oxide layer to the dielectriccap.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as embodiments of the invention isparticularly pointed out and distinctly claimed in the claims at theconclusion of the specification. The foregoing and other advantages ofthe embodiments of the invention are apparent from the followingdetailed description taken in conjunction with the accompanying drawingsin which:

FIGS. 1A-20C illustrate exemplary methods of making semiconductordevices according to embodiments, in which:

FIG. 1A is top view of fins patterned in a substrate;

FIG. 1B is a cross-sectional side view through the X-X′ axis of FIG. 1A;

FIG. 2A is a top view after depositing a dummy gate material on thefins;

FIG. 2B is a cross-sectional side view through the X-X′ axis of FIG. 2A;

FIG. 3A is a top view after forming dummy gates;

FIG. 3B is a cross-sectional side view through the X-X′ axis of FIG. 3A;

FIG. 3C is a cross-sectional side view through the Y-Y′ axis of FIG. 3A;

FIG. 4A is a top view after forming source/drains;

FIG. 4B is a cross-sectional side view through the X-X′ axis of FIG. 4A;

FIG. 4C is a cross-sectional side view through the Y-Y′ axis of FIG. 4A;

FIG. 5A is a top view after depositing a first oxide around the dummygates;

FIG. 5B is a cross-sectional side view through the X-X′ axis of FIG. 5A;

FIG. 5C is a cross-sectional side view through the Y-Y′ axis of FIG. 5A;

FIG. 6A is a top view after recessing the first oxide and depositing asecond oxide;

FIG. 6B is a cross-sectional side view through the X-X′ axis of FIG. 6A;

FIG. 6C is a cross-sectional side view through the Y-Y′ axis of FIG. 6A;

FIG. 7A is a top view after removing the dummy gate hard mask;

FIG. 7B is a cross-sectional side view through the X-X′ axis of FIG. 7A;

FIG. 7C is a cross-sectional side view through the Y-Y′ axis of FIG. 7A;

FIG. 8A is a top view after patterning a first stage of dummy gatematerial removal;

FIG. 8B is a cross-sectional side view through the X-X′ axis of FIG. 8A;

FIG. 8C is a cross-sectional side view through the Y-Y′ axis of FIG. 8A;

FIG. 9A is a top view after removing a first stage of dummy gatematerial and over etching through the oxide layer to form firsttrenches;

FIG. 9B is a cross-sectional side view through the X-X′ axis of FIG. 9A;

FIG. 9C is a cross-sectional side view through the Y-Y′ axis of FIG. 9A;

FIG. 10A is a top view after filling the first trenches with metals andremoving the mask;

FIG. 10B is a cross-sectional side view through the X-X′ axis of FIG.10A;

FIG. 10C is a cross-sectional side view through the Y-Y′ axis of FIG.10A;

FIG. 11A is a top view after recessing the metal fill in the firsttrenches and depositing a dielectric material;

FIG. 11B is a cross-sectional side view through the X-X′ axis of FIG.11A;

FIG. 11C is a cross-sectional side view through the Y-Y′ axis of FIG.11A;

FIG. 12A is a top view after patterning a second stage of dummy gatematerial removal;

FIG. 12B is a cross-sectional side view through the X-X′ axis of FIG.12A;

FIG. 12C is a cross-sectional side view through the Y-Y′ axis of FIG.12A;

FIG. 13A is a top view after removing the second stage of dummy gatematerial to form second trenches;

FIG. 13B is a cross-sectional side view through the X-X′ axis of FIG.13A;

FIG. 13C is a cross-sectional side view through the Y-Y′ axis of FIG.13A;

FIG. 14A is a top view after filling the first trenches with metals andremoving the mask;

FIG. 14B is a cross-sectional side view through the X-X′ axis of FIG.14A;

FIG. 14C is a cross-sectional side view through the Y-Y′ axis of FIG.14A;

FIG. 15A is a top view after recessing the metal fill in the secondtrenches and depositing a dielectric material;

FIG. 15B is a cross-sectional side view through the X-X′ axis of FIG.15A;

FIG. 15C is a cross-sectional side view through the Y-Y′ axis of FIG.15A;

FIG. 16A is a top view after patterning a gate contact;

FIG. 16B is a cross-sectional side view through the X-X′ axis of FIG.16A;

FIG. 16C is a cross-sectional side view through the Y-Y′ axis of FIG.16A;

FIG. 17A is a top view after filling the gate contact;

FIG. 17B is a cross-sectional side view through the X-X′ axis of FIG.17A;

FIG. 17C is a cross-sectional side view through the Y-Y′ axis of FIG.17A;

FIG. 18A is a top view after recessing the gate contact filling andforming a dielectric gate cap;

FIG. 18B is a cross-sectional side view through the X-X′ axis of FIG.18A;

FIG. 18C is a cross-sectional side view through the Y-Y′ axis of FIG.18A;

FIG. 19A is a top view after patterning the source/drain contacts

FIG. 19B is a cross-sectional side view through the X-X′ axis of FIG.19A;

FIG. 19C is a cross-sectional side view through the Y-Y′ axis of FIG.19A;

FIG. 20A is a top view after filling the source/drain contact trenches;

FIG. 20B is a cross-sectional side view through the X-X′ axis of FIG.20A;

FIG. 20C is a cross-sectional side view through the Y-Y′ axis of FIG.20A;

FIG. 21A-21D illustrate methods for forming contacts to the independentgates of the device in FIG. 20B according to embodiments, in which:

FIG. 21A is a cross-sectional side view after flipping the structureshown in FIG. 20B and bonding to a substrate;

FIG. 21B is a cross-sectional side view after forming metal contactlayer on the back side of the device;

FIG. 21C is a cross-sectional side view after flipping the device againand bonding to another substrate; and

FIG. 21D is a cross-sectional side view after forming contacts to bothgate portions;

FIGS. 22A and 22B illustrate methods for forming contacts to theindependent gates of the device of FIG. 20B according to embodiments, inwhich:

FIG. 22A is a cross-sectional side view after forming a first contactthrough the oxide layer; and

FIG. 22B is a cross-sectional side view after flipping the device andforming a second backside contact;

FIGS. 23A-23C illustrate methods for forming a device according toembodiments, in which:

FIG. 23A is a cross-sectional side view of an initial structure in whicha metal layer is bonded to patterned fins (combining a metal layer withFIG. 1B);

FIG. 23B is a cross-sectional side view after following the process flowshown in FIGS. 2A-20C; and

FIG. 23C is a cross-sectional side view after forming contacts to theindependent gates.

DETAILED DESCRIPTION

Embodiments of the present invention are described herein with referenceto the related drawings. Alternative embodiments can be devised withoutdeparting from the scope of this invention. It is noted that variousconnections and positional relationships (e.g., over, below, adjacent,etc.) are set forth between elements in the following description and inthe drawings. These connections and/or positional relationships, unlessspecified otherwise, can be direct or indirect, and the presentinvention is not intended to be limiting in this respect. Accordingly, acoupling of entities can refer to either a direct or an indirectcoupling, and a positional relationship between entities can be a director indirect positional relationship. As an example of an indirectpositional relationship, references in the present description toforming layer “A” over layer “B” include situations in which one or moreintermediate layers (e.g., layer “C”) is between layer “A” and layer “B”as long as the relevant characteristics and functionalities of layer “A”and layer “B” are not substantially changed by the intermediatelayer(s).

The following definitions and abbreviations are to be used for theinterpretation of the claims and the specification. As used herein, theterms “comprises,” “comprising,” “includes,” “including,” “has,”“having,” “contains” or “containing,” or any other variation thereof,are intended to cover a non-exclusive inclusion. For example, acomposition, a mixture, process, method, article, or apparatus thatcomprises a list of elements is not necessarily limited to only thoseelements but can include other elements not expressly listed or inherentto such composition, mixture, process, method, article, or apparatus.

Additionally, the term “exemplary” is used herein to mean “serving as anexample, instance or illustration.” Any embodiment or design describedherein as “exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments or designs. The terms “at least one”and “one or more” are understood to include any integer number greaterthan or equal to one, i.e. one, two, three, four, etc. The terms “aplurality” are understood to include any integer number greater than orequal to two, i.e. two, three, four, five, etc. The term “connection”can include an indirect “connection” and a direct “connection.”

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedcan include a particular feature or characteristic, but every embodimentmay or may not include the particular structure or characteristic.Moreover, such phrases are not necessarily referring to the sameembodiment. Further, when a particular structure or characteristic isdescribed in connection with an embodiment, it is submitted that it iswithin the knowledge of one skilled in the art to affect such structureor characteristic in connection with other embodiments whether or notexplicitly described.

For purposes of the description hereinafter, the terms “upper,” “lower,”“right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” andderivatives thereof shall relate to the described structures andmethods, as oriented in the drawing figures. The terms “overlying,”“atop,” “on top,” “positioned on” or “positioned atop” mean that a firstelement, such as a first structure, is present on a second element, suchas a second structure, wherein intervening elements such as an interfacestructure can be present between the first element and the secondelement. The term “direct contact” means that a first element, such as afirst structure, and a second element, such as a second structure, areconnected without any intermediary conducting, insulating orsemiconductor layers at the interface of the two elements. It should benoted that the term “selective to,” such as, for example, “a firstelement selective to a second element,” means that the first element canbe etched and the second element can act as an etch stop.

As used herein, the terms “about,” “substantially,” “approximately,” andvariations thereof are intended to include the degree of errorassociated with measurement of the particular quantity based upon theequipment available at the time of filing the application. For example,“about” can include a range of ±8% or 5%, or 2% of a given value.

For the sake of brevity, conventional techniques related tosemiconductor device and integrated circuit (IC) fabrication may or maynot be described in detail herein. Moreover, the various tasks andprocess steps described herein can be incorporated into a morecomprehensive procedure or process having additional steps orfunctionality not described in detail herein. In particular, varioussteps in the manufacture of semiconductor devices andsemiconductor-based ICs are well known and so, in the interest ofbrevity, many conventional steps will only be mentioned briefly hereinor will be omitted entirely without providing the well-known processdetails.

Turning now to a description of technologies that are more specificallyrelevant to aspects of the present invention, independent gate FETs areuseful for voltage tuning in analog applications. Independent gatesallow for independent gate control on either side of the channel. Mixersand current amplifiers can benefit from independent gate implementation.Independent functionality of device gates also can enable exploration ofnovel digital logic.

However, forming independent gates has been limited to FinFET deviceswith single individual fins. For devices with multiple fins, it ischallenging to wire the corresponding gates together, while maintainingthe wiring for the source and drains in scaled technologies.

Accordingly, described herein are process flows and devices that utilizethe backside of the device to provide a wiring path for the additionalgate. Replacement gate processing is performed in two stages to formindependent gate electrodes. A first gate process uses over etching tomaking an opening through the oxide layer to an underlying gate wire.The methods spatially separate the contact layer for the independentgates, forming one gate above the device and one gate below the device.In embodiments, by forming a gate resembling an interdigitated comb,every other gate can be routed in the traditional form above the device,or through the oxide layer below the device. In embodiments, apre-existing underlying gate wire can eliminate post device waferbonding and thinning.

Turning now to a detailed description of aspects of the presentinvention, FIGS. 1A-20C illustrate exemplary methods of makingsemiconductor devices according to embodiments. FIG. 1A is top view offins 100 patterned in a substrate 101. FIG. 1B is a cross-sectional sideview through the X-X′ axis of FIG. 1A. Non-limiting examples ofsubstrate 101 materials include Si (silicon), strained Si, SiC (siliconcarbide), Ge (germanium), SiGe (silicon germanium), SiGeC(silicon-germanium-carbon), Si alloys, Ge alloys, III-V materials (e.g.,GaAs (gallium arsenide), InAs (indium arsenide), InP (indium phosphide),or aluminum arsenide (AlAs)), II-VI materials (e.g., CdSe (cadmiumselenide), CdS (cadmium sulfide), CdTe (cadmium telluride), ZnO (zincoxide), ZnSe (zinc selenide), ZnS (zinc sulfide), or ZnTe (zinctelluride)), or any combination thereof.

The substrate 101 includes an oxide layer 102. The composition of theoxide layer 102 depends on the composition of the substrate 101, as wellas prior treatments performed on the substrate 101. The oxide layer 102can be, for example, silicon dioxide (SiO₂). In another example, thesubstrate 101 includes germanium, and the oxide layer 102 includesgermanium dioxide (GeO₂). In a further example, the substrate 101includes GaAs, and the oxide layer 102 includes Ga₂O₃, As₂O₃, As₂O₅, orany combination thereof.

The fins 100 include hard mask caps 103 that protect the fins 100 duringsubsequent processing. The hard mask caps 103 include, for example,silicon nitride, in one or more embodiments. In other embodiments, thehard mask caps 103 include another hard mask material.

The fins 100 can be formed in the substrate 101 after initiallydepositing the hard mask material forming the hard mask caps 103 on thesubstrate 101. The fins 100 can be patterned in the substrate 101 by,for example, sidewall imaging transfer. Any number of fins 100 can beformed in the substrate 101, including more than one fin to form aplurality of fins. Six fins are only shown for illustrative purposes. Aplurality of fins 100 arranged on the substrate 101 includes more thanone fin 100. The fins of the plurality of fins are arranged on the oxidelayer 102.

FIG. 2A is a top view after depositing a dummy gate material 202 on andaround the fins 100. FIG. 2B is a cross-sectional side view through theX-X′ axis of FIG. 2A. The dummy gate material 202 (or sacrificial gatematerial) will be subsequently replaced with a metal gate stack to formthe final metal gates. The dummy gate material 202 is a sacrificialmaterial, for example, amorphous silicon (aSi) or polycrystallinesilicon (polysilicon). The dummy gate material 202 can be deposited by adeposition process, including, but not limited to, physical vapordeposition (PVD), chemical vapor deposition (CVD), plasma enhancedchemical vapor deposition (PECVD), inductively coupled plasma chemicalvapor deposition (ICP CVD), or any combination thereof.

Dummy oxides 203 are formed around the fins 100. A dummy material isdeposited on the fins 100. The dummy oxide 203 protects the fins 100during etching (see, for example, FIGS. 9A-9C). Non-limiting examples ofsuitable materials for the dummy oxide 203 include dielectric oxides(e.g., silicon oxide), dielectric nitrides (e.g., silicon nitride),dielectric oxynitrides, or any combination thereof.

FIG. 3A is a top view after patterning dummy gates 330. FIG. 3B is across-sectional side view through the X-X′ axis of FIG. 3A. FIG. 3C is across-sectional side view through the Y-Y′ axis of FIG. 3A. The dummygates 330 include a hard mask layer 301 for example, silicon nitride(SiN), SiOCN, or SiBCN. The hard mask layer 301 is deposited on thedummy gate material 202 to form gate caps. The hard mask layer 301 canbe deposited using a deposition process, including, but not limited to,PVD, CVD, PECVD, or any combination thereof. The dummy gate material 202and hard mask material 301 is then patterned and etched to form thedummy gates 330.

Gate spacers 302 are formed along sidewalls of the dummy gates 330. Adielectric material, for example, silicon dioxide, silicon nitride,SiOCN, or SiBCN, is deposited on the dummy gate material 202 and thenetched to form gate spacers 302. Other non-limiting examples ofmaterials for the gate spacers 302 include dielectric oxides (e.g.,silicon oxide), dielectric nitrides (e.g., silicon nitride), dielectricoxynitrides, or any combination thereof. The gate spacer 302 material isdeposited by a deposition process, for example, chemical vapordeposition (CVD) or physical vapor deposition (PVD). An anisotropic dryetch process, for example, reactive ion etch (RIE), is performed to etchthe spacer material and form gate spacers 302 around the dummy gates330.

FIG. 4A is a top view after forming source/drains on opposing sides ofthe dummy gates 330. FIG. 4B is a cross-sectional side view through theX-X′ axis of FIG. 4A. FIG. 4C is a cross-sectional side view through theY-Y′ axis of FIG. 4A. Before forming the source/drains 405, thesubstrate 101 material and the spacer 302 material is etched (as shownin FIG. 4C) around the dummy gates 330. The source/drains 405 can beformed by epitaxially growing a semiconductor material layer on thesubstrate 101 around the dummy gates 330. Epitaxial layers forming thesource/drains 405 can be grown using a suitable growth process, forexample, chemical vapor deposition (CVD) (liquid phase (LP) or reducedpressure chemical vapor deposition (RPCVD), vapor-phase epitaxy (VPE),molecular-beam epitaxy (MBE), liquid-phase epitaxy (LPE), metal organicchemical vapor deposition (MOCVD), or other suitable processes.Alternatively, the source/drains 405 can be formed by incorporatingdopants into the substrate 101.

FIG. 5A is a top view after depositing a first oxide 501 around thedummy gates 330. FIG. 5B is a cross-sectional side view through the X-X′axis of FIG. 5A. FIG. 5C is a cross-sectional side view through the Y-Y′axis of FIG. 5A. The first oxide 501 covers the source/drains 405 andfills the spaces between the dummy gates 330. The first oxide 501 isdeposited on the dummy gates 330. Then a planarization process isperformed, for example, chemical mechanical planarization (CMP) down tothe level of the hard mask layer 301 such that the hard mask layer 301is exposed. The first oxide 501 can be, but not limited to, siliconoxide, spin-on-glass, a flowable oxide (FOX), a high density plasmaoxide, borophosphosilicate glass (BPSG), or any combination thereof.

FIG. 6A is a top view after recessing the first oxide 501 and depositinga second oxide 602 on the recessed first oxide 501. FIG. 6B is across-sectional side view through the X-X′ axis of FIG. 6A. FIG. 6C is across-sectional side view through the Y-Y′ axis of FIG. 6A. The secondoxide 602 can be, but not limited to, silicon oxide, spin-on-glass, aflowable oxide (FOX), a high density plasma oxide, borophosphosilicateglass (BPSG), or any combination thereof. After depositing the secondoxide 602 on the first oxide 501 and the dummy gates 330, aplanarization process is performed, for example, CMP, stopping on thehard mask layer 301.

FIG. 7A is a top view after removing the dummy gate hard mask layer 301.FIG. 7B is a cross-sectional side view through the X-X′ axis of FIG. 7A.FIG. 7C is a cross-sectional side view through the Y-Y′ axis of FIG. 7A.The hard mask layer 301 and a portion of the second oxide 602 areremoved by etching, for example, by reactive ion etching (RIE). Anotheretch process, or a planarization process, such as CMP, can be performedto remove the remainder of the hard mask layer 301, stopping on thedummy gate material 202.

FIG. 8A is a top view after patterning a first stage of dummy gatematerial removal. FIG. 8B is a cross-sectional side view through theX-X′ axis of FIG. 8A. FIG. 8C is a cross-sectional side view through theY-Y′ axis of FIG. 8A. As will be subsequently described, removing thedummy gate material and replacing with a metal gate is performed in twostages. The first stage is described in FIGS. 8A-11C. The second stageis described in FIGS. 12A-15C. Two stages are performed to formindependent gate electrodes.

A patterning mask 808 is deposited on the substrate 101. The mask 808can include an organic material, for example, a polymeric material. Themask 808 is patterned over at least one dummy gate 330, such that atleast one opening 809 is formed over the dummy gate 330. Alignment ofthe opening 809 is critical at this stage because the opening, forexample as shown in FIG. 8B must be arranged between fins 100. In otherwords, the opening 809 in the mask 808 should be properly aligned toprotect the fins 100 so that when the dummy gate material 202 is removedthrough the openings 809, the fins 100 are not damaged. Although thespacer 203 material around each fins protect the fins 100, alignment ofthe mask 808 is important. The thickness of the spacer 203 material canalso be tailored or increased to provide additional protection.

FIG. 9A is a top view after removing a first stage of dummy gatematerial 202 removal and over etching through the oxide layer 102 toform first trenches 909. FIG. 9B is a cross-sectional side view throughthe X-X′ axis of FIG. 9A. FIG. 9C is a cross-sectional side view throughthe Y-Y′ axis of FIG. 9A. The first trenches 909 are over etched toextend through the oxide layer 102 to a top surface of the substrate 101(see FIG. 9B). Each first trench 909 is arranged between fins 100 of theplurality of fins 100. One or more etch processes can be performed toremove portions of both the dummy gate material 202 and the oxide layer102. The first trenches extend from the substrate 101 to the top of thedummy gate material 202.

FIG. 10A is a top view after filling the first trenches 909 with metalsto form a first portion 1030 of the final independent metal gates andremoving the mask 808. FIG. 10B is a cross-sectional side view throughthe X-X′ axis of FIG. 10A. FIG. 10C is a cross-sectional side viewthrough the Y-Y′ axis of FIG. 10A. The first portion 1030 of the finalindependent metal gates include one or more dielectric layers 1001 and agate stack 1002 that includes one or more work function metals and gatemetals. The gate dielectric layer(s) 1001 can be a dielectric materialhaving a dielectric constant greater than about 3.9, about 7.0, or about10.0. Non-limiting examples of suitable materials for the dielectriclayers 1001 include oxides, nitrides, oxynitrides, silicates (e.g.,metal silicates), aluminates, titanates, nitrides, or any combinationthereof. Examples of high-k materials (with a dielectric constantgreater than 7.0) include, but are not limited to, metal oxides such ashafnium oxide, hafnium silicon oxide, hafnium silicon oxynitride,lanthanum oxide, lanthanum aluminum oxide, zirconium oxide, zirconiumsilicon oxide, zirconium silicon oxynitride, tantalum oxide, titaniumoxide, barium strontium titanium oxide, barium titanium oxide, strontiumtitanium oxide, yttrium oxide, aluminum oxide, lead scandium tantalumoxide, and lead zinc niobate. The high-k material can further includedopants such as, for example, lanthanum and aluminum.

The work function metal of the gate stack 1002 is disposed over thedielectric layers 1001. The type of work function metal(s) depends onthe type of transistor. Non-limiting examples of suitable work functionmetals include p-type work function metal materials and n-type workfunction metal materials. P-type work function materials includecompositions such as ruthenium, palladium, platinum, cobalt, nickel, andconductive metal oxides, or any combination thereof. N-type metalmaterials include compositions such as hafnium, zirconium, titanium,tantalum, aluminum, metal carbides (e.g., hafnium carbide, zirconiumcarbide, titanium carbide, and aluminum carbide), aluminides, or anycombination thereof.

The conductive gate metal of the gate stack 1002 is deposited over thework function layer(s) to form the gate stacks. Non-limiting examples ofsuitable conductive metals include aluminum (Al), platinum (Pt), gold(Au), tungsten (W), titanium (Ti), or any combination thereof. Aplanarization process, such as CMP, is performed to polish the surfaceof the metal gates.

FIG. 11A is a top view after recessing the metal fill of the gate stack1002 and depositing a dielectric material 1102. FIG. 11B is across-sectional side view through the X-X′ axis of FIG. 11A. FIG. 11C isa cross-sectional side view through the Y-Y′ axis of FIG. 11A. The gatestack 1002 can be recessed by etching. The dielectric material 1102 canbe, for example, silicon nitride (SiN), SiOCN, or SiBCN. Afterdepositing the dielectric material 1102, a planarization process, suchas CMP, is performed.

FIG. 12A is a top view after patterning a second stage of dummy gatematerial 202 removal. FIG. 12B is a cross-sectional side view throughthe X-X′ axis of FIG. 12A. FIG. 12C is a cross-sectional side viewthrough the Y-Y′ axis of FIG. 12A. The second stage of dummy gatematerial removal 202 provides an alternate gate pattern that isdifferent (and independent from) the first stage shown above to form thefirst portion 1030 of the final metal gates (see FIGS. 11A-11C). Thefirst stage and the second stages form gates that function independentlyof one another.

Another patterning mask 1203 is deposited on the substrate 101. The mask1203 can include an organic material, for example, a polymeric material.The mask 1203 is patterned over the same dummy gate that was patternedin the first stage such that at least one opening 1209 is formed.Alignment of the opening 1209 is less critical than in the first stagebecause the dielectric material 1102 cap protects the first portion 103of the final metal gates.

FIG. 13A is a top view after removing the second stage of dummy gatematerial 202 to form second trenches 1301. FIG. 13B is a cross-sectionalside view through the X-X′ axis of FIG. 13A. FIG. 13C is across-sectional side view through the Y-Y′ axis of FIG. 13A. Unlike thefirst trenches 909 formed in FIGS. 9A-9C, the second trenches 1301 arenot over etched through the oxide layer 102. Instead the dummy gatematerial 202 is removed down to the level of the oxide layer 102,stopping on the oxide layer 102. The second trenches 1301 thus extendfrom a top surface of the oxide layer 102. A bottom surface of thesecond trenches 1301 are arranged over a bottom surface of the firsttrenches 909 (see FIG. 9B). The second trenches 1301 are arrangedbetween the fins 100 of the plurality of fins and alternate with thefirst trenches 909.

FIG. 14A is a top view after filling the second trenches 1301 withmetals and removing the mask 1203 to form the second portions 1430 ofthe final metal gates. FIG. 14B is a cross-sectional side view throughthe X-X′ axis of FIG. 14A. FIG. 14C is a cross-sectional side viewthrough the Y-Y′ axis of FIG. 14A. The second portion 1430 of the finalindependent metal gates include one or more dielectric layers 1404 and agate stack 1403 that includes one or more work function metals and gatemetals. The gate dielectric layer(s) 1404 and the gate stack 1403 caninclude one or more of the materials described above for the firstportion 1030 of the final independent metal gates.

FIG. 15A is a top view after recessing the metal fill of the gate stack1404 and depositing a dielectric material 1505. FIG. 15B is across-sectional side view through the X-X′ axis of FIG. 15A. FIG. 15C isa cross-sectional side view through the Y-Y′ axis of FIG. 15A. The gatestack 1508 can be recessed by etching. The dielectric material 1505 canbe, for example, the dielectric material 1102 described above. Afterdepositing the dielectric material 1505, a planarization process, suchas CMP, is performed.

As shown, first portions 1030 and second portions 1430 of the finalindependent metal gates are formed. The first portions 1030 and thesecond portions 1430 will function as independent gates, with one abovethe final device and one below the final device, depending on theorientation. Contacts will be formed to the first portions 1030, belowthe gate structures, and the second portions 1430, above the gatestructures (see embodiments shown in FIGS. 21A-23C).

FIG. 16A is a top view after patterning a gate contact to connect thefirst portions 1030 of the gate. FIG. 16B is a cross-sectional side viewthrough the X-X′ axis of FIG. 16A. FIG. 16C is a cross-sectional sideview through the Y-Y′ axis of FIG. 16A. A trench is etched over themetal gate stacks of the first portions 1030 and the second portions1430. Etching is performed to remove a portion of dielectric layers1102, 1505 (see FIG. 15B). Because first portions 1030 of the final gatesit lower than second portions 1430, the dielectric layers 1102, 1505,do not sit at the same height. Therefore, when a dielectric etch isperformed, some of dielectric layer 1102 remains after etching. All orsubstantially all of the dielectric layers 1505 is removed.

FIG. 17A is a top view after filling the gate contact with metal(s)1707. FIG. 17B is a cross-sectional side view through the X-X′ axis ofFIG. 17A. FIG. 17C is a cross-sectional side view through the Y-Y′ axisof FIG. 17A. One or more metal layers can be deposited to connect thesecond portions 1430 as shown. The one or more metal layers aredeposited on the dielectric material 1102 of the first portions 1030.The metal(s) can be the same as or different than the metals used in thefirst portions 1030 and the second portions 1430 described above. Theresulting metal contact including metal(s) 1707 connect the secondportions 1430 of the gates and is arranged over the dielectric caps ofthe first portions 1030. The dielectric caps of the first portions 1030(including dielectric material 1102) isolate the first portions 1030from the second portions 1430 so that the first portions 1030 canfunction independently of the second portions.

FIG. 18A is a top view after recessing the gate contact filling andforming a dielectric gate cap 1808. FIG. 18B is a cross-sectional sideview through the X-X′ axis of FIG. 18A. FIG. 18C is a cross-sectionalside view through the Y-Y′ axis of FIG. 18A. The gate contact filling(metal(s) 1707) can be recessed by etching, and then a dielectricmaterial is deposited on the recessed metals to form the dielectric cap1808. The dielectric material can be, but is not limited silicon nitride(SiN), SiOCN, or SiBCN.

FIG. 19A is a top view after patterning the source/drain contacts. FIG.19B is a cross-sectional side view through the X-X′ axis of FIG. 19A.FIG. 19C is a cross-sectional side view through the Y-Y′ axis of FIG.19A. An oxide layer 1909 is deposited on the substrate and patternedover the source/drains 405 to form openings over the source/drains 405.Non-limiting examples of materials for the oxide layer 1909 includesilicon dioxide, tetraethylorthosilicate (TEOS) oxide, high aspect ratioplasma (HARP) oxide, high temperature oxide (HTO), high density plasma(HDP) oxide, oxides (e.g., silicon oxides) formed by an atomic layerdeposition (ALD) process, or any combination thereof.

FIG. 20A is a top view after filling the source/drain contact trenches(openings) with contact metal(s) 2000. FIG. 20B is a cross-sectionalside view through the X-X′ axis of FIG. 20A. FIG. 20C is across-sectional side view through the Y-Y′ axis of FIG. 20A. The contactmetal(s) 2000 can include a liner layer, which can include a low contactresistance material, conductive liner material, or alloy. Non-limitingexamples of suitable low contact resistance materials include titanium,titanium nitride, tantalum, tantalum nitride, tungsten, niobium, cobalt,cobalt titanium, nickel, platinum, or any combination thereof. One ormore conductive metals are then deposited on the liner. The conductivemetal can be, but is not limited to, aluminum (Al), platinum (Pt), gold(Au), tungsten (W), titanium (Ti), or any combination thereof. Aplanarization process, for example, CMP, is then performed.

The resulting devices shown in FIGS. 20A-20C provide a gate withalternating first and second gate portions beneath a protectivedielectric cap 1808 on a top surface of the gate. The first portions1030 are arranged below the second portions, with the first portionscontacting the substrate 101 and extending through the oxide layer 102.The second portions 1430 extend from a top surface of the oxide layer102 to the dielectric cap 1808 and are connected by a layer of metalbeneath the dielectric cap. After forming the structures shown in FIGS.20A-20C, several methods can be used to integrate the dual independentgate structure with additional metal layers to form contacts above andbelow the device. FIGS. 21A-21C, FIGS. 22A and 22B, and FIGS. 23A-23Cillustrate various methods. However, embodiments are not limited tothese examples.

FIG. 21A-21D illustrate methods for combining the structure of FIG. 20Bwith another metal layer to form contacts according to one or moreembodiments. FIG. 21A is a cross-sectional side view after flipping thestructure shown in FIG. 20B (device 2110) upside down and bonding to asubstrate 2103. After flipping the device 2110, first portions 1030 ofthe final gate extend over the second portions 1430. A temporary bondingfilm 2102 can be applied between the substrate 2103 and the device 2110.

FIG. 21B is a cross-sectional side view after forming another metallayer 2104 to the back side of the device. The original substrate 101 isremoved, and a second metal layer 2104 is formed to connect firstportions 1030 of the gate. The second metal layer 2104 includes one ormore conductive metals and is formed within a dielectric layer 2105.

FIG. 21C is a cross-sectional side view after flipping the device upsidedown again and bonding to another substrate 2106 and temporary (orpermanent) bonding film 2105. FIG. 21D is a cross-sectional side viewafter forming contacts to both gates. A first contact 2107 connects tothe metal layer 2104, and a second contact 2108 connects to secondportions 1430 of the gate. The second contact 2108 above the gate isshorter than the first contact 2107 below the gate. The metal layer 2104contacts and connects bottom surfaces of first portions 1030 of thegate. The first contact 2107 is arranged adjacent to the gate. Thesecond contact 2108 extends through the dielectric cap 1808 on the gate.

FIGS. 22A and 22B illustrate methods for combining the structure of FIG.20B with another metal layer level to form contacts according to one ormore embodiments. FIG. 22A is a cross-sectional side view after forminga first contact 2207 through the oxide layer 102. FIG. 22B is across-sectional side view after flipping the device and forming a secondmetal layer 2208 in a dielectric layer 2209. The second metal layer 2208connects top surfaces of second portions 1430 of the gate. The devicecan be bonded to a substrate 2206 and a temporary (or permanent) bondingfilm 2205. The first contact 2207 is also extended through thedielectric layer 2209.

FIGS. 23A-23C illustrate methods for forming a device according to oneor more embodiments. FIG. 23A is a cross-sectional side view of aninitial structure in which a metal layer 2303 is formed beforepatterning fins 100 (combining a metal layer 2303 with FIG. 1B). Inthese embodiments, a metal layer 2303 in a dielectric layer 2302 iscombined with patterned fins 100. The process flows described above inFIGS. 2A-20C are then performed. FIG. 23B is a cross-sectional side viewafter following the processing in FIGS. 2A-20C. FIG. 23C is across-sectional side view after forming contacts. First contact 2307extends to the metal layer 2303, and second contact extends to thesecond portions 1430 of the dual gate structure. In contrast to theembodiments shown in FIGS. 21A-22B, no flipping of the device is needed.The metal layer 2303 can be formed first and a new device layer can bedeposited, grown, or transferred on top of the metal layer 2303.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments described. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdescribed herein.

What is claimed is:
 1. A semiconductor device, comprising: a metallayer, an oxide layer arranged on the metal layer; a fin arranged on themetal layer; a gate stack formed on the fin and extending substantiallyperpendicular to the fin, the gate comprising a dielectric cap on a topsurface of the gate stack, the gate stack comprising alternating firstportions and second portions, the first portions arranged below thesecond portions, the first portions contacting the metal layer andextending through the oxide layer to a dielectric layer arranged beneathand separate from the dielectric cap, and the second portions extendingfrom a top surface of the oxide layer to the dielectric cap, the metallayer arranged beneath and in contact with bottom surfaces of the firstportions of the gate.
 2. The semiconductor device of claim 1, furthercomprising source/drains arranged on opposing sides of the gate stack.3. The semiconductor device of claim 2, wherein the source/drainscomprise epitaxially grown semiconductor material.
 4. The semiconductordevice of claim 1, wherein a contact is arranged adjacent to the gate.5. The semiconductor device of claim 4, further comprising anothercontact extending through the dielectric cap to the gate stack.
 6. Thesemiconductor device of claim 1, wherein the dielectric layer of thefirst portions of the gate stack are silicon nitride (SiN), SiOCN, orSiBCN.
 7. A semiconductor device, comprising: a substrate; an oxidelayer arranged on the substrate; a fin arranged on the substrate; a gatestack formed on the fin and extending substantially perpendicular to thefin, the gate stack comprising a dielectric cap on a top surface of thegate stack, the gate stack comprising alternating first portions andsecond portions, the first portions arranged below the second portions,the first portions contacting a metal layer and extending through theoxide layer to a dielectric layer arranged beneath and separate from thedielectric cap, and the second portions extending from a top surface ofthe oxide layer to the dielectric cap; and a gate contact arranged overthe first portions and second portions of the gate that connects thesecond portions of the gate.
 8. The semiconductor device of claim 7,further comprising source/drains arranged on opposing sides of the gatestack.
 9. The semiconductor device of claim 8, wherein the source/drainscomprise epitaxially grown semiconductor material.
 10. The semiconductordevice of claim 7, wherein the dielectric layer of the first portions ofthe gate are silicon nitride (SiN), SiOCN, or SiBCN.